Distributed Raman Optical Amplification in Phase Coherent Transfer of Optical Frequencies

摘要

We describe the application of Raman optical-fiber\udamplification (ROA) for the phase coherent transfer of optical\udfrequencies in an optical fiber link. ROA uses the transmission\udfiber itself as a gain medium for bi-directional coherent\udamplification. In a test setup, we evaluated the ROA in terms\udof ON/OFF gain, signal-to-noise ratio, and phase noise added\udto the carrier. We transferred a laser frequency in a 200 km\udoptical fiber link, and evaluated both co-propagating and counterpropagating\udamplification pump schemes. Then, we identified the\udoccurrence of nonlinearities on the signal for non-optimized ROA\udgain. The frequency at the remote end has a fractional frequency\udinstability of 3 · 10−19 over 1000 s with the optical fiber link\udnoise compensation.